Note: Descriptions are shown in the official language in which they were submitted.
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SILICONE FOAM CONTROL AGENT
This invention is concerned with silicone foam
control agents and with cornpositions containing them.
In many aqueous systems which are used e.g. in food
processes, textile dying, paper production, sewage treat-
ment and cleaning applications, surface active agents are
present either as an unwanted ingredient or as deliberately
introduced materials to achieve a certain function. Due to
the presence of these surface active agents foam is often
generated. In certain applications, such as in dish
washing by hand, this is a welcome effect but in other
applications foam generation can lead to unsatisfactory
results. This is for example the case in the dyeing of
textiles or in the manufacture of paper. In other appli-
cations, for example the use of detergent compositions for
domestic laundering, the production of foam needs to be
controlled rather than avoided. It is important to keep
the foam formation to an acceptable level, especially when
laundering is performed in automatic front loading washing
machines. Excessive foam would cause overflow of the
washing liquor onto the floor as well as reduction in the
efficiency of the laundering operation itself.
Foam control agents are known in such industries and
have been incorporated into for example heavy duty
detergent powders for use in automatic washing machines.
Silicone foam control agents are regarded as very effective
in this application as they can be added in very small
quantities and are not affected by e.g. the hardness of
water, while traditional foam control compositions, such as
soaps, require a certain water hardness for their
effectiveness.
2 ~ 7 ~
The detergent industry is currently going through an
important evolution where, due to environmental concern and
energy conservation efforts, there is a move towards the
use of detergent compositions which will perform ade~uately
at lower laundering temperatures. One way in which this is
achieved is by the increase of the surfactant level in the
detergent compositions. Anionic surfactants are especially
favoured. Unfortunately these surfactants usually create
more foam than for example the nonionic surfactants. Since
silicone foam control agents do not directly contribute to
the cleaning power of a detergent composition it is
desirable to keep the addition level of such foam control
agents to a minimum. There has therefore arisen a need to
develop improved foam control agents for incorporation in
detergent compositions.
Silicone foam control agents containing branched
siloxanes are known in the art. E.P. patent specification
0 217 501 describes a foam control agent wherein a liquid
siloxane component is obtained by mixing 100 parts by
weight of a polydiorganosiloxane having triorganosiloxane
end-groups, 10 to 125 parts of a polydiorganosiloxane
having at least one terminal silanol group and at least 40
silicon atoms and 0.5 to 10 parts of an organopolysiloxane
resin comprising monofunctional and tetrafunctional
siloxane units in a ratio of from 0.5:1 to 1.2:1, and
having at least one silanol group per molecule, and there-
after heating the mixture. The specification describes the
need to control the amount of resin used in order to retain
a liquid polymer, avoid,ing a gel structure. This indicates
that some branching occurs in the siloxane component of the
foam control agent. Although foam control agents according
to E.P. 0 217 501 perform adequately in many applications,
there is a continuing search for improved foam control
agents.
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European Patent Application 0 273 448 discloses a
foam suppressant composition made by the free radical
polymerisation of a polydiorganosiloxane, silica, a pendant
vinyl functional silicone oil and a free radical polymeri-
sation initiator such as benzoyl peroxide. This reaction
is carried out at elevated temperature, which reaction
cannot be guaranteed to be safe. It is also difficùlt to
control this reaction. It is required in the European
Application 0 273 448 that the highly viscous reaction
product be diluted with a low viscosity polysiloxane in
order to form an effective antifoam end product.
~ he present invention provides a foam control agent
which is an improvement over the silicone foam control
agent of E.P. 0 217 501 with regard to efficiency. The
process is also safer than that used for the manufacture of
the silicone anti~oam ot` E.P. 0 273 448. No dilution of a
reaction product is required in order to formulate a final
foam control agent. This is significant in that it
eliminates a costly and time consuming process step in the
manufacture of an end product.
The present invention also differs significantly from
that described in the prior art. The reagents used are
very different from those of E.P. 0 217 501 and although
vinyl functional siloxanes are used, as is the case in the
European Application 0 273 448, instead of a pendant vinyl
functional silicone oil the present invention uses a vinyl
endblocked polydiorganosiloxane. ~lurther differences
between the present invention and that set forth in E.P.
0 273 448 are the choice of the second reagent and of the
catalyst. Where E.P. o 273 ~8 utilises a free radical
polymerisation initiator such as benzoyl peroxide the
instant invention provides for crosslinking with an organo-
hydrogensiloxane in the presence of a noble metal catalyst.
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The use of hydrosilylation ~ se is not new in the
production of foam control agents. U.S. 4,741,861
discloses a silicon based antifoam composition comprising
among other ingredients a dioryanopolysiloxane terminated
at both molecular chain ends with a vinyldiorganosilyl
group and a diorganopolysiloxane terminated at both mole-
cular chain ends with a diorganosilyl group. The two types
of diorganopolysiloxane are reacted in the presence of a
platinum compound to provide a polymer of higher viscosity
through chain extension. There is no indication in the
prior art that providing a branched polydiorganosiloxane
through hydrosilylation would result in improved foam
control agents.
The invention provides in one of its aspects a method
for preparing a silicone foam control agent which comprises
the steps of (A) forming a mixture of a vinyl end-blocked
polydiorganosiloxane, a volatile, low viscosity organo-
hydrogensiloxane having at least 3 silicon-bonded hydrogen
atoms and a solvent, (B) reacting said mixture in the
presence of a noble metal catalyst to make a branched
organopolysiloxane and (C) adding to the mixture a finely
divided particulate material having a surface rendered
hydrophobic by contact with a treating agent.
Vinyl end-blocked polydiorganosiloxanes which are
useful in step (A) of the method of the invention have the
general formula Vi-[Si(R2)o]n-Si(R2)Vi, wherein R denotes
an organic group and Vi denotes a vinyl group. The organic
group R is preferably a hydrocarbon group of up to 8 carbon
atoms, more preferably an al~cyl group or an aryl group,
e.g. methyl, ethyl, propyl, hexyl or phenyl. It is most
preferred that at least 80% of all R groups are methyl
groups. The value of _, which denotes an integer, is such
that the viscosity of the vinyl end-blocked
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polydiorganosiloxane is in the range of from 200 to 100,000
mPa.s, more preferably 2000 to 55,000 mPa.s at a tempe-
rature of 25C.
In step (A) of a method according to the invention
the volatile low viscosity organohydrogensiloxane may be a
cyclic or linear material, and may be a mixture including
both cyclic and linear organohydrogensiloxanes. Suitable
cyclic organohydrogensiloxanes include those of the formula
(R'HSio)X in which R' is an alkyl or aryl radical having
from 1 to 6 carbon atoms preerably methyl, and x is an
integer from 3 to 5. Suitable linear low viscosity
volatile organohydrogensiloxanes include those of the
general formula R'l3SiG(R'HSio)ySiRll3 where R' is the same
as above, R" denotes either H or R' and y is from 2 to 9,
provided there are at least 3 silicon-bonded hydrogen atoms
per molecule.
In step (~) of the method according to the invention
a solvent is employed which is preferably a polydiorgano-
siloxane. Suitable polydiorganosiloxane solvents aresubstantially linear polymers wherein the silicon~bonded
substituents are groups R, as defined above. Most prefer-
ably at least 80% of all silicon-bonded substituents are
methyl groups. Most preferred so]vents include trimethyl-
siloxy end-blocked polydimethylsiloxanes having a viscosity
of 500 to 12500 mPa.s measured at 25C. The solvents are
mainly present to solubilise the brallched polydiorgano-
siloxane made in step (B) of the method of the invention.
The nob:Le metal catalyst for use in step (B) of the
method of the invention catalyses the hydrosilylation
reaction and may be selected from a variety of hydrosily-
lation catalysts ]cnown to promote the reaction of vinyl-
functional radicals with silicon-bonded hydrogen atoms.
Suitable noble metal catalysts include platinum and
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rhodium-containing compounds and complexes. Platinum
catalysts such as platinum acetylacetonate or
chloroplatinic acid are representative of these compounds
and suitable for use. A preferred catalyst mixture is a
chloroplatinic acid complex of divinyltetramethyldisiloxane
diluted in dimethylvinylsiloxy endhlocked polydimethyl-
siloxane which may be prepared according to methods
described by Willing in U.S. patent No. 3,419,593. Most
preferably this mixture contains about 0.6 weight percent
platinum.
Hydrosilylation catalysts are well known in the art
and the interested reader is referred to the following
patents for detailed descriptions regarding their
preparation and use: Speier, U.S. Patent No. 2,823,218;
Willing, U.S. Patent No. 3,419,359; Kookootsedes, U.S.
Patent No. 3,445,420; Polmanteer et al, U.S. Patent No.
3,697,473; Nitzsche, U.S. Ratent No. 3,814,731; Chandra,
U.S. Patent No. 3,890,359 and Sandford, U.S. Patent No.
4,123,604. Many of the catalysts known in the art require
the reactants to be heated in order for a reaction to
occur. When such catalysts are employed this requirement
must be taken into consideration.
The branched organopolysiloxane prepared in step (B)
of the method according to the present invention has a
three dimensional network and preferably has a viscosity of
500 to 500,000 m.Pa.s measured at 25C, more preferably
5000 to 50,000 m.Pa.s. F`or purposes of foam control agents
according to the present invention, the branched organo-
polysiloxane should most preferably have a viscosity ofabout 20,000 m.Pa.s measured at 25C.
When platinum catalysts are used in step (B) of the
method of the invention an inhibitor may be required in
order to improve the shelf life of the starting materials
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and to control the viscosity-time profile of the compo-
sitions. These inhibitors are also known in the art and
include ethylenically unsaturated isocyanurates, such as
trialkylisocyanurate, dialkylacetylenedicarboxylates, alkyl
maleates, phosphine, phosphites, aminoalkyl silanes,
sulphoxides, acrylonitrile derivatives and others.
Particular inhibitors preferably used are diethyl fumarate,
bis(2-methoxy-l-methylene)maleate, bis(2-methoxy-1-methyl-
ethyl)maleate and similar compounds.
All of these materials are well known in the art andare commercially available products.
In its simplest terms, the reaction for forming the
branched three dimensional network organopolysiloxane in
step (B) of the method of the present invention can be
characterised as:
l l Pt
-SiCH=CH2 + HSi- ------> -SiCH2CH2Si-
The reaction may be carried out in any convenient way but
we prefer to blend the vinyl endblocked polydiorgano-
siloxane, volatile low viscosity organohydrogensiloxane,
solvent and noble metal catalyst and to carry out the
reaction at a temperature of 30 to 100C preferably 70C.
Preferably, the vinyl endblocked polydiorganosiloxane is
included in the reactant solution in an amount of from 5 to
20% by weight and the volatile low viscosity organohy-
droyensiloxane is employed in an amount of from 0.01 to 3~,
more preferably 0.04 to 1% by weicJht of the solution used
in step (~). The concentrations of catalyst and inhibitor
to be used in the present invention may be determined by
routine experimentation. Typically, the effective amount
of catalyst should be in a ranye so as to provide from
about 0.1 to 1000 parts per million (ppm) of platinum by
9 2~7~6~
weight in the compositions of the present invention. As an
example, when the preferred catalyst mixture ti.e. the
chloroplatinic acid complex of divinyltetramethyldisiloxane
containing about 0.6% by weight of platinum) and inhibitor
(i.e. bis(2-methoxy-1-methylethyl~maleate) are employed, a
ratio by weight of inhibitor to catalyst mixture ranging
from zero to about 0.6 provides a suitably wide range of
inhibition which is adequate under most practical
conditions of manufacture.
A foam control agent according to the present
invention preferably also comprises a polyorganosiloxane
fluid and advantageously this may be provided by the poly-
diorganosiloxane solvent employed in the method of
preparing the branched polyorganosiloxane.
The finely divided particulate materials used in step
(C) of the method of the inventlon may be any of the known
inorganic fillers suitable for formulating foam control
agents. Such fillers are described in many patent appli-
cations. They include fumed Tio2/ ~12O3, aluminosilicates,zinc oxide, magnesium oxide, salts of aliphatic carboxylic
acids, reaction products of isocyanates with certain
materials, e.g. cyclohexylamine, alkyl amides, e.g.
ethylene or methylene bis stearamide and sio2 with a
surface area as measured by BET measurement of at least 50
m2/g. Preferred fillers are silica fillers which can be
made according to any oE the standard manufacturing
techniques for example thermal decomposition of a silicon
halide, a decomposition and precipitation of a metal salt
of silicic acid, e.g. sodium silicate and a gel formation
method. Suitable silicas for use in a method according to
this invention include therefore fumed silica, precipitated
silica and gel ~ormation silica. ~he average particle size
of these fillers may range Erom 0.1 to 20 ~ but preferably
is from 0.5 to 2.5 ~.
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The surface of filler particles is rendered hydro-
phobic in order to mak2 the foam control agents suffi-
ciently effective in aqueous systems. Rendering the filler
particles hydrophobic may be done either prior to or after
dispersing the filler particles in the liquid silo~ane
obtained in step (A) or step (B) of the method of the
invention. This can be effected by treatment of the filler
particles with treating agents, e.g. reactive silanes or
siloxanes, for example dimethyldichlorosilane, trimethyl-
chlorosilane, hexamethyldisilazane, hydroxy-endblocked and
methyl-endblocked polydimethylsiloxanes and siloxane
resins. Fillers which have already been treated with such
compounds are commercially available from many companies,
for example Sipernat~ D10 from Degussa. The surface of the
filler may alternatively be rendered hydrophobic ln situ,
i.e. after the filler has been dispersed in the liquid
siloxane component. This may be effected by adding to the
liquid siloxane component prior to, during or after the
dispersion of the filler e.g. duriny step (A) of the method
of invention, the appropriate amount of a treating agent,
of the kind described above, and heating the mixture to a
temperature above 40C. The quantity of treating agent to
be employed will depend for example on the nature of the
agent and the filler and will be evident or ascertainable
by those skilled in the art. Sufficient should be employed
to endow the Eiller with at least a discernible degree of
hydrophobicity. The filler is added to the foam control
agents in an amount of about 1 to 15, preferably 3 to 5% by
weight.
The invention provides in another of its aspects a
foam control agent made by the method of the invention as
described above.
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The foam control agents of this invention are useful
for reducing or preventing foam formation in aqueous
systems. Such foam contro:L agents are particularly useful
for reducing the foam generated by detergent compositions,
especially during ]aundering operations. The foam control
agent may be incorporated in a detergent composition in any
of the known ways, for example in emulsion form or in a
form wherein it is protected against degradation during for
example storage, such as in encapsulated form. Such
methods are well known in the art and have been disclosed
in a number of patent specifications. The advantage of
foam control agents produced by the method of this
invention is greatest when the composition is used in a
detergent composition which has a high foaming ability.
However, they can also be incorporated in other detergent
compositions. Such detergent compositions are known in the
art and are described in many patents.
The foam control agents of the invention are there-
fore particularly useful when incorporated in thosedetergent compositions where a high level of high foaming
surfactants is present, for example anionic surfactants,
e.g. sodium dodecyl benzene sulphonate. High levels of
anionic surfactants may be used to ensure effectiveness of
detergent composition at lower washing temperatures, e.g.
40C.
In yet another aspect of the invention there is
provided a detergent composition comprising (1) 100 parts
by weight of a detergent component and (2) from 0.05 to 5
parts by weight of a foam control agent according to the
invention.
Suitahle detergent components comprise an active
detergent, organic and inorganic builder salts and other
additives and diluents. The active detergent may comprise
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organic detergent surfactants oE the anionic, cationic,
non-ionic or amphoteric type, or mlxtures thereof. Suit-
able anionic organic detergent surfactants are alkali metal
soaps of higher fatty acids, al]~yl aryl sulphonates, for
example sodium dodecyl benzene sulphonate, long chain
(fatty) alcohol sulphates, olefine sulphates and sulpho-
nates, sulphated monoglycerides, sulphated ethers, sulpho-
succinates, alkane sulphonates, phosphate esters, alkyl
isothionates, sucrose esters and fluorosurfactants. Suit-
able cationic organic detergent surfactants are alkylamine
salts, quaternary ammonium salts, sulphonium salts and
phosphonium salts. Suitable non-ionic organic surfactants
are condensates of ethylene oxide with a long chain ~fatty)
alcohol or fatty acid, for example C14 15 alcohol,
condensed with 7 moles of ethylene oxide (Dobanol 45-7),
condensates of ethylene oxide with an amine or an amide,
condensation products of ethylene and propylene oxides,
fatty acid alkylol amide and fatty amine oxides. Suitable
amphoteric organic detergent surfactants are imidazoline
compounds, alkylaminoacid salts and betaines. Examples of
inorganic components are phosphates and polyphosphates,
silicates, such as sodium silicates, carbonates, sulphates,
oxygen releasing compounds, such as sodium perborate and
other bleaching agents and zeolites. Examples of organic
components are anti-redeposition agents such as carboxy-
methylcellulose (CMC), bri~hteners, chelating agents, such
as ethylene diamine tetraacetic acid (EDT~) and nitrilotri-
acetic acid (NTA), enzymes and bacteriostats. Materials
suitable for the detergent component are well known to the
person skilled in the art, and are described in many text
books, for example Synthetic Detergents, A. Davidsohn and
B.M. Milwidsky, 6th edition, George Godwin (1978).
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The following examples illustrate the invention. All
parts and percentages are expressed by weight unless other-
wise stated.
Example I
Into a reaction vessel there was added 850 grams of
lO00 mPa.s trimethylsiloxy endblocked polydimethylsiloxane
solvent. To the vessel there was added chloroplatinic acid
(H2PtCl6.6H2O) in the amount of lO 4 moles of platinum per
mole of SiH as catalyst and 150 grams of a vinyl endblocked
polydimethylsiloxane having a viscosity of 9500 mPa.s. As
crosslinking agent there was added to the vessel 0.04% by
weight based on the weight oE the composition of cyclic and
linear organohydrogensiloxanes as a mixture including the
tetramer and pentamer. The vessel was heated to 70C and
the organohydrogensiloxane crosslinking agent was added to
the vessel until the viscosity of the fluid in the vessel
reached a viscosity of 2000 mPa.s. A gel-formation silica
treated with hexamethyldisilazane was added to the fluid in
the vessel in an amount of 5% by weight of fluid. The
product in the vessel was used in a detergent antifoam
composition and tested for its foam suppression
capabilities as described in Example II.
Example I~
A conventional automatic washing machine ~Miele 427)
of the front loading type, having a transparent loading
door was loaded with 3.5kg oE clean cotton fabric. A wash
cycle with a prewash and a main wash (95C) was carried out
using one lot of a commercial detergent powder having no
foam control agent present, for each of the prewash and the
main wash.
Each lot of detergent powder consisted of lOOg of a
high foaming detergent powder which comprised linear alkyl
sulphonate, alkyl dimethylamine oxide, silicate, sodium
a 6 ~
tripolyphosphate, sodium perborate and sodium sulphate and
a foam control agent prepared in accordance with Example I.
The door of the washing machine ~as divided in its height
by a scale of from 0 to ~00% with 10~ intervals. The foam
height during the wash cycle was recorded at one minute
intervals from the beginning of the wash cycle. The
recording was done when the rotation drum of the washing
machine was stationary. Higher values indicate a higher
foam level and thus a worse performance of the fcam control
composition. Values between 30 to ~0 indicate that there
was no foam formed in the wash drum. Values between 120
and 130 indicate that the foam level in the wash drum
filled about one-half of the drum. Values of 180 to 240 or
above indicate that the foam filled the drum and that the
foam overflowed the machine. The test results indicated in
Table I show the highest level of ~~oam obtained during the
wash cycle.
Table I shows the amount of foam control agent
contained in the detergent powders tested. Six different
foam control agents were prepared following the procedure
set forth in Example I, and these six foam control agents
were added to detergent powders in amounts from 0.05 to 0.2
percent by weight based on the total weight of the deter-
gent powder. The foam control agents which were preparedfollowing the procedure in Example I are iclentified in
Table Ia showing the amount of the trimethylsiloxy end-
blocked polydimethylsiloxane (PDMS) used, along with its
viscosity and the amount of the vinyl endblocked polydi-
methylsiloxane (Vi) used along with its viscosity.
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ABLE I
Foam Heights
Weight % Foam Control
Aqent in the Deterqent
0.2 0.13 0 1 O.G8 0.06 0.05
Foam
Control Aqent
(1) 32 33 51 111 200 200
(2) 39 32 80 92 200 200
(3) 43 40 43 56 81 110
(4) 33 37 68 73 72 125
(5) 40 31 57 95 200 200
(6) 51 40 60 90 200 200
CA 39 114 129 200 200 200
In Table I the "Comparative Antifoam" (CA) is a
commercially available antifoam formulation which was
tested in order to provide a comparison with the antifoam
compositions of the present invention. The "Comparative
Antifoam" was a three dimensional gel network made
according to the teachings of E.P. 0 217 501.
Table Ia
Foam Control ~qent Composition
Aaent PDMS PDMS Vi Vi
% n~Pa.s % mPa.s
(1) 90 3000 ~.0 55000
(2) 90 5000 10 55000
(3) 85 1000 15 9500
(4) 90 3000 10 9500
(5) 85 500 15 55000
(6) 85 500 15 9500
It should be apparent from a consideration of Table I
that the foam control agents prepared in accordance with
the present invention possess superior foam suppressing
35 characteristics in comparison to commercially available
antifoam products.
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It should be noted that the applicant of the herein
described present invention considers the method of manu-
facturing products in accordance with the previously
mentioned E.P. O 273 448 to be of a hazardous nature
because of the high temperatures required for polymeri-
sation and the formation of toxic volatile materials such
as formaldehyde and volatile flammables. Therefore no
comparative data were generated with the compositions
10 described in the E.P. O 273 448.
